The present invention relates to ophthalmic lenses made from polymeric compositions. More particularly, the invention relates to ophthalmic lenses, preferably deformable intraocular lenses, having reduced surface tackiness made from acrylate and/or methacrylate-based polymeric compositions.
Intraocular lenses (IOLs) have been known for a long time, since shortly after the end of World War II. Such a lens is surgically implanted into a mammalian eye, e.g., human eye, to replace a damaged or diseased natural lens of the eye and restore the patient""s vision.
Although IOLs are made from xe2x80x9chardxe2x80x9d or xe2x80x9crigidxe2x80x9d polymeric or glass optical materials, such as polymethyl methacrylate (which has a refractive index of 1.49), soft resilient polymeric materials, such as silicones, have been increasingly used, for the reasons discussed below, in ophthalmic applications.
Since soft IOLs are deformable, for example, foldable or rollable, for implantation, a smaller incision can be surgically cut in the eye than for the implantation of xe2x80x9chardxe2x80x9d IOLs of the same optical power. The smaller the incision, the less trauma the patient""s eye experiences and the faster post-operative healing occurs. An incision of about 3 mm is ideal since this size incision is presently required to remove the natural lens after it has been broken up, for example, emulsified in a conventional phaceoemulsification procedure. In contrast the typical IOL optic has a diameter of about 6 mm.
The size and mechanical characteristics of the deformable IOLs play an important role. As is well understood by those skilled in the art, for successful implantation, the deformable IOL must have sufficient structural integrity, elasticity and elongation and be small enough in size to permit deforming for insertion through a small incision. After insertion, the lens must, of course, regain its original shape and have sufficient structural integrity to retain such shape under normal use conditions.
In general, the thinner the deformable IOL the smaller the incision in the eye that is required. On the other hand, in order to function optically as an IOL, the lens must have sufficient optical refractory power. Also, the higher the optical refractive index of the material making up the IOL, the thinner the IOL can be and still obtain the same optical refractory power.
Deformable IOLs made of acrylic materials can be quite tacky in nature, which tackiness inhibits deforming to a sufficiently small size for insertion through a very small incision and/or may cause handling problems
Gupta U.S. Pat. No. 4,834,750 discloses IOLs with optics made of copolymers of methacrylate esters which form homopolymers that are relatively hard at room temperature and acrylate esters which form homopolymers that are relatively soft at room temperature. Such copolymers are cross-linked with a diacrylate ester to produce an acrylate material which preferably includes a constituent derived from a fluoroacrylate to reduce surface tackiness. None of the specific monomers disclosed in this patent provide homopolymers which have a refractive index of at least about 1.50.
Weinschenk, III U.S. Pat. No. 5,331,073 discloses acrylic-based intraocular lenses which optionally include a constituent derived from a hydrophilic monomeric component. This constituent is effective to reduce the tackiness of the copolymer. However, such hydrophilic constituent may cause a disadvantageous decrease in the index of refraction of the final IOL optic in that some water is included within the copolymer.
LeBoeuf et al U.S. Pat. No. 5,603,774 discloses plasma treatment of the polymer surface to reduce tackiness associated with certain acrylic polymers, particularly those polymers useful in intraocular lenses. However, such plasma treatment does involve an additional manufacturing step. Also, the non-homogeneous intraocular lens which results from the surface being treated with plasma has the potential of causing problems in the eye.
It would be advantageous to provide ophthalmic lens materials of construction which have good optical properties, including optical clarity and high refractive index (index of refraction) and, in addition, have reduced tackiness without the disadvantages of the prior art materials noted above.
New polymeric materials and ophthalmic lenses, for example, IOLs, produced from such polymeric materials have been discovered. The present polymeric materials are derived from a combination of monomers and provide very useful optical properties in terms of optical clarity and high index of refraction and can be formed into ophthalmic lenses, for example, optics of IOLs which are effectively deformable, preferably foldable, for insertion through small surgical incisions, preferably on the order of about 3 mm or less (in maximum transverse dimension). Importantly, the present compositions and ophthalmic lenses have reduced surface tackiness without requiring the presence of fluoroacrylates, hydrophilic components and without requiring plasma treatment. By selecting the monomeric components used to produce the present compositions and ophthalmic lenses in accordance with the present invention, reduced surface tackiness is achieved with little or no adverse impact on the optical clarity, refractive index, homogeneity, biocompatability, deformability, and cost of production of such compositions and ophthalmic lenses. The present compositions and lenses can be produced using conventional techniques, e.g., conventional polymerization techniques. Thus, the present invention is very effective and easy to practice and results in polymeric compositions and ophthalmic lenses which have outstanding properties.
In one broad aspect of the present invention, ophthalmic lens bodies are provided which comprise cross-linked polymeric materials or compositions. Such materials comprise a first constituent derived from a first monomeric component selected from acrylates, methacrylates and mixtures thereof. A second constituent is included and is derived from a second component in an amount effective as a cross linker in the cross-linked polymeric material. The cross-linked polymeric material has branched chain alkyl groups in an amount effective to reduce the tackiness of the cross-linked polymeric material relative to a substantially identical cross-linked polymeric material without the branched chain alkyl groups. It has been found that the inclusion of branched chain alkyl groups, for example, in the first monomeric component, or portion thereof, unexpectedly provides reduced surface tackiness to the cross-linked polymeric material. Thus, this reduced tackiness is obtained without requiring the presence of a fluoroacrylate or a hydrophilic component and without requiring treating, for example, plasma treating, the surface of the polymeric material.
The present ophthalmic lens bodies may be in the form of optics of IOLs, contact lenses, corneal implants (for example, corneal onlays and corneal inlays) and other ophthalmic lens bodies. The present lens bodies are particularly useful as optics of IOLs, more preferably deformable IOLs. Because a deformable IOL is adapted to be deformed, that is rolled, folded or otherwise deformed, prior to insertion into the eye, it is important that the IOL optic have a relatively reduced degree of surface tackiness to provide for effective deforming for insertion and/or to allow the optic to effectively regain its original shape in the eye.
The term xe2x80x9cbranched chain alkyl groupsxe2x80x9d, as used herein, refers to alkyl groups which are non-linear. Thus, at least one, and preferably more than one, carbon atom in the alkyl group is located in one or more branches, rather than being located in a single linear portion of the alkyl group. Also, cycloalkyl groups are, by definition, branched chain alkyl groups. The branched chain alkyl group may be of any size suitable to function as described herein. Preferably, the branched chain alkyl group has about 3 to about 20 carbon atoms and more preferably about 6 to about 15 carbon atoms.
The amount of branched chain alkyl groups present is sufficient to provide a cross-linked polymeric material having reduced tackiness relative to a substantially identical cross-linked polymeric material without the branched chain alkyl groups. The monomeric component, for example, the first monomeric component, or portion thereof, including the branched chain alkyl groups used in providing the present cross-linked polymeric materials may represent a wide ranging proportion of the total monomeric components employed. Preferably, the branched chain alkyl group-containing monomeric component, or portion thereof, provides a constituent of the cross-linked polymeric materials which is present in an amount in the range of about 1% or less to about 50% or more, and more preferably about 3% to about 25%, by weight of the cross-linked polymeric material.
The first monomeric component, or at least a portion thereof, preferably is selected from acrylates including a branched chain alkyl group, methacrylates including a branched chain alkyl group and mixtures thereof. In one useful embodiment, the cross-linked polymeric material includes a third constituent derived from a third monomeric component other than the first and second monomeric components. This third monomeric component is selected from acrylates, methacrylates and mixtures thereof. Preferably, the first monomeric component is selected from acrylates having a branched chain alkyl group and mixtures thereof. The third monomeric component preferably is selected from methacrylates and mixtures thereof.
In one embodiment the present cross-linked polymeric material has reduced tackiness relative to a substantially identical cross-linked polymeric material in which the first constituent is replaced by a constituent derived from a monomeric component having a straight chain alkyl group having the same number of carbon atoms as the branched chain alkyl groups of the first monomeric component.
Advantageously, the cross-linked polymeric material has an index of refraction of at least about 1.50. Relatively high indexes of refraction allow the ophthalmic lenses, and in particular IOLs, to be conveniently manufactured with relatively high optical powers and the capability of being passed through scleral tunnel incisions of about 3.0 mm or even about 2.8 mm or less. Preferably, the cross-linked polymeric material includes aryl-containing groups in an amount effective to increase the index of refraction of the cross-linked polymeric material relative to the index of refraction of a substantially identical cross-linked polymeric material without the aryl-containing groups. In a very useful embodiment, the third monomeric component includes an effective amount of aryl-containing groups to increase the index of refraction of the cross-linked polymeric material, as desired.
In order to provide the desired degree of deformability, the cross-linked polymeric material preferably has a glass transition temperature (Tg) of about 22xc2x0 C. or less. Thus, in the context of an IOL optic, a cross-linked polymeric material having a Tg within this preferred range can be folded or otherwise deformed for insertion at or about room temperature.
Each individual feature and each combination of two or more features described herein are included within the scope of the present invention provided that the features included in the combination are not mutually inconsistent.
These and other aspects of the present invention are set forth in the following detailed description, examples and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.